With the conventional linear motion guide units of roller type, lubrication members are installed in the end caps lying at opposite ends in the sliding direction of the slider to apply lubricant around the rolling elements inside the turnaround passages in the end caps, thereby to accomplish maintenance-free operation for lubrication. In Japanese Laid-Open Patent Application No. 2007-100 951 which is a commonly-assigned senior application, for example, there is disclosed a linear motion guide unit having lubricant resupply means in which application of lubricant around the rolling elements is done at the turnaround passage to make the lubrication system simpler than ever in construction, along with maintenance-free for steady and positive lubrication. With the prior linear motion guide unit constructed as stated earlier, the end cap has an opening extending from a recess on the outward end surface to the turnaround passage and a lubricant reservoir plate of porous compact impregnated with lubricant fits into the recess on the outward end surface of the end cap. The lubricant reservoir plate has an applicator nose extending through the opening in the end cap to form at the extremity thereof in part the circular wall of the turnaround passage to expose itself to come into engagement with the rollers rolling through the turnaround passage, thereby making application of lubricant around the rollers.
In another Japanese Laid-Open Patent Application No. 2010-14 228 which is also a commonly-assigned senior application, there is disclosed a linear rolling motion guide unit in which the race or raceway groove of the guide rail may be applied or coated uniformly or evenly with lubricant whether the guide rail is kept at any posture of horizontal, vertical, tilt or upside down. With the linear rolling motion guide unit constructed as stated just earlier, the member body which fits over or conforms to the guide rail has the embedding portion recessed or concaved to accommodate therein the lubricant-impregnated member to apply the lubricant on the race or raceway groove of the guide rail. The embedding portion of the member body fitting over the guide rail has at least a part maintained in position at a level equal or higher than the level of at least a part of one of the races of the guide rail located higher relative to the other races. Thus, it will be said that the prior linear rolling motion guide unit constructed as stated earlier. as having an additional lubricating member supplied with lubricant later on, may continue to apply lubricant on the guide rail while keeping positive engagement with the guide rail whether the guide rail is kept at any posture of horizontal, vertical, tilt or upside down.
Another Japanese Laid-Open Patent Application No. 2004-36 814 discloses a linear motion guide unit having lubricant supplier means which is able to be supplied with lubricant to make it possible to continue to keep steady lubrication for a prolonged interval of time. With the prior linear motion guide unit, the lubricant supplier means is placed to come close to the member to be applied with lubricant and composed of a shell layer of polymer containing lubricant therein and a lubricant retainer layer holding lubricant therein. The shell layer comes into engagement or contact at least in part with the member to be lubricated, and the lubricant retainer layer is made of needle felt that fits into a concave formed inside the shell layer. The needle felt is composed of synthetic resin fibers where grease or lubricant is absorbed so as to be resupplied.
Meanwhile, though the conventional linear motion guide units have been expected to continue application of lubricant around the rolling elements over a prolonged interval of time to realize the maintenance-free working for lubrication, there has been ever developed no lubricant supplier means good enough to continue supplying lubricant around the rolling elements over a prolonged interval of time to realize the maintenance-free working for lubrication. With some prior linear motion guide units, there has been developed the sleeve construction of lubricant supplier means. However, the sleeve construction, as very thin in thickness, becomes too less in volume to keep sufficient amount of lubricant. Thus, there is a fear of poor lubrication such as binding between rolling elements or sticky condition which would be caused by lubrication lack around the rolling elements. Moreover, although there is provided the linear motion guide unit of roller type in which porous compact impregnated with lubricant fits into the end cap and applicator noses extend to expose themselves to the turnaround passages to carry out application of the lubricant around rolling elements from the inside circular surfaces of the turnaround passages while rollers roll across the turnaround passage, the linear motion guide unit constructed as stated just earlier has a major problem that the structure becomes very sophisticated.
With the linear motion guide unit of such type that the lubricating member makes contact with the raceway surface of the guide rail, there is a major challenge that the lubricating member suffers with much frictional resistance because of resupply of lubricant and correspondingly is worn down to gradually change in contact condition, causing poor lubricating condition. When lubricant-containing polymer is selected for the lubricating member, the lubricant-containing polymer is manufactured by the steps of melting the mixture of polyolefin polymer with lubricating material of poly a olefin oil or the like and pouring molten mixture into a desired mould to solidify the molded mixture while cooling under pressure. The lubricant-containing polymer swells because the resinous material itself has absorbed the lubricating material, but shrinks with deformation after the lubricating material has been discharged. As a result, there will be fear of a serious issue that the lubricant-containing polymer suffers more shrinkage than the reinforcing member with the result that the supply of the lubricating agent around the rolling elements is hindered.